In the automobile industry, research studies are carried out to improve mileage according to a growing global interest in the environment and energy, and other studies of downsizing, high-functioning and reducing a weight are also carried out to satisfy various consumers' demands. In particular, various research and developments of a hybrid vehicle using engine power and electric energy are being increased.
The hybrid vehicle mainly selects an idle stop/go system in which an engine thereof is automatically stopped when the vehicle is stopped during waiting the signal and then restarted by operating a transmission. However, an air conditioner of the hybrid vehicle is operated by the engine. If the engine is stopped, a compressor is also stopped and thus a temperature of an evaporator is increased. Therefore, there is a problem that a driver may feel inconvenience. Further, since refrigerant in the evaporator can be easily vaporized at a room temperature, the refrigerant is vaporized during a short period while the compressor is stopped. Although the engine is restarted and the compressor and evaporator are operated again, the vaporized refrigerant should be compressed and liquefied again. Therefore, there are other problems that it takes long time for supplying a chilly wind and energy consumption is increased.
Meanwhile, in order to improve a cooling efficiency, there was proposed Japanese Patent Laid-Open No. 2000-205777 entitled “Thermal energy storage heat exchanger” which is shown in FIG. 1. As shown in FIG. 1, in the thermal energy reserving heat exchanger, a heat exchanging medium passage 191e through which a heat exchanging medium is flowed and a thermal energy reserving material chamber 191f, 191f′ for storing thermal energy reserving material are integrally formed with a dual structural tube 191, and a passage 194 for fluid which is heat-exchanged with the heat exchanging medium is formed outside the dual structural tube 191.
However, in the thermal energy reserving heat exchanger as shown in FIG. 1, since the dual structural tube 191 is formed by coupling a plurality of plate materials, coupling defects are occurred with increasing frequency and it is difficult to fabricate the tube. Further, if the coupling defects are occurred, the heat exchanging medium and the thermal energy reserving material may be mixed. Furthermore, it is difficult to find a portion where the coupling defects are occurred.
Moreover, since the passage through which the heat exchanging medium is flowed is formed outside the dual structural tube and the thermal energy reserving material chamber for storing the thermal energy reserving material is formed inside the dual structural tube, it is facile to store the cold of the heat exchanging medium in the thermal energy reserving material. However, since the air passing through the outside of the dual structural tube is contacted with the thermal energy reserving material chamber, there is other problem that a rate of heat transfer of the heat exchanging medium is lowered. And since fins disposed outside the dual structural tube are just contacted with the thermal energy reserving material chamber and is not directly connected to the heat exchanging medium passage, the efficiency in heat exchange is lowered.